1. Field of the Invention
The present invention generally relates to an electromagnetic clutch and more particularly a clutch using curved flat leaf springs to transmit torque and permit axial flexibility of the axially movable component of the clutch, together with a key and notch drive connection to enable limited relative rotational movement between the inner and outer ends of the springs thereby assuring that the springs will not be deflected beyond their elastic limit during high torque startup of the compressor of an air conditioning unit in an automobile.
2. Description of the Prior Art
In the development of electromagnetic clutches for driving air conditioning compressors in an automobile, my prior U.S. Pat. No. 3,565,223 issued Feb. 23, 1971, discloses one structure which has been known for a number of years in which flat leaf springs are used to transmit torque and a resilient insert is incorporated into the hub to provide flexibility or resiliency in the drive connection to the input shaft of the compressor. Prior U.S. Pat. No. 3,205,989, issued Sept. 14, 1965, discloses another type of electromagnetic clutch using similar straight flat leaf springs and a resilient coupling in the drive train. While such devices have operated satisfactorily, it is noted that the resilient insert arrangements utilizing rubber or some other resilient plastic material materially increases the over-all length and other dimensional characteristics of the clutch and, of course, increases the weight of the clutch as well as the cost thereof, all of which are desired to be maintained at a minimum. In both of the prior art patents mentioned above and in other similar devices on the market, a pulley is driven from a belt connecting with the crank shaft or other rotatable component of an internal combustion engine and drives the input shaft of a compressor through a magnetic clutch and a resilient coupling. Basically, the magnetic clutch includes an axially movable armature disk connected to the hub of the clutch through flat leaf springs which enables axial movement of the armature disk and transmits torque to the hub which is connected to the input shaft. The armature disk is attracted to a friction face on the rotatable pulley through an energizable magnetic coil. Also, a resilient insert is interposed in the drive coupling between the pulley and input shaft of the compressor to prevent binding of the compressor shaft or rotor. The previously patented and existing electromagnetic clutches are somewhat bulky, include many components, are relatively heavy and have a substantial over-all length.